This ancient system of underground passageways now totals more than 150 miles, making it the 7th longest cave on Earth. It contains more of the fabled boxwork formation than all other caves combined. A quick look at the geology of Wind Cave reveals how this unique cave system formed.
Guide to Wind Cave
Born Under the Sea
The caverns of Wind Cave originated in limestone deposits on a warm shallow seafloor some 350 million years ago. Large amounts of gypsum (calcium sulfate) formed within recesses in the limestone and over time, began to swell and shrink as they absorbed and expelled water. As the gypsum swelled, it created cracks in the surrounding limestone and slowly worked itself into these cracks where it eventually crystalized.
First Passageways
As the shallow seas retreated, more acidic freshwater was introduced into the rocks, which reacted with the gypsum, converting it into calcite. This created a byproduct of sulfuric acid, which dissolved surrounding limestone. This process created the first passageways of Wind Cave, some 320 million years ago, and would be repeated many times over the next 240 million years, slowly forming a cave system.
Uplift
Somewhere around 40-60 million years ago, the Black Hills area experienced a significant geologic uplift due to the forces of plate tectonics. This caused significant fractures in the limestone, and the process of cave building increased rapidly. Water here did not flow through the cave, as it did in Kentucky’s Mammoth Cave, instead it sat, soaking the limestone and slowly worked its erosive magic, enlarging small cracks and sinking further into the depths, creating deeper fissures and a complex vertical maze.
Boxwork Forms
The waters that filled this cave slowly began to drain an estimated 40 million years ago, exposing the numerous cracks on the cave’s walls and ceilings that were filled with the crystalized remains of the gypsum, which first began to separate the limestone some 250 million years before. These rare formations came to be known as boxwork.
A World Class Cave
The unique structure produced by this natural subterranean process created one of the most complex vertical cave systems in the world. Wind Cave is home to a known 154 miles of known passageways that lie below a mere 1.25 square miles of land. The amount of box work found here far outweighs that found in all other cave systems combined.
The Caves Today
Exploration of the Wind Cave continues, and an average of about 2 miles of new passageways are found every year. There are more than 3,000 unexplored openings that have yet to be explored, so any estimate of the total measure of this bizarre cave system is far from realistic.
A system of lakes have been discovered nearly 500′ below the surface. Within this environment which has never seen the light of day, there are more than 4,000 species of diverse bacteria, many of which are unique to Wind Cave. The study of these bacteria are of great interest to the scientific community, as many of these unique lifeforms may one day become useful to the medical field.
Guide to Wind Cave
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